Specialized mass spectrometry analyses are provided to the laboratory and to other collaborating units. The emphasis of this work is split between identification of trace organic compounds isolated from biological sources and the mass spectrometry of biopolymers (e.g. peptides, proteins and oligonucleotides). A very close working relationship and collaboration is maintained with the Laboratory of Biophysical Chemistry, NHLBI, especially with the research into, and use of techniques for, mass spectrometry of macromolecules. Approval has been received to upgrade the electrospray source on the JEOL SX1O2 instrument to enhance stability and sensitivity, and to facilitate interfacing to liquid chromatographic methods. This will be used as part of the Unit's effort into post-translational modifications of proteins. The capillary zone electrophoresis instrument continues to receive heavy usage from this laboratory and an investigator from BEIP. Use is made of the NHLBI laser desorption mass spectrometer for the analysis of proteins, protein digests and oligonucleotides as part of our growing work in biopolymer mass spectrometry. Using a combination of this instrument and the JEOL mass spectrometer, methods have been developed and applied for the determination and identification of disulfide bonds in proteins, and for the analysis of oligonucleotides and DNA by mass spectrometry. In the small molecule area, collaborative interest has continued in the identification of biologically active natural products, especially those of interest in AIDS research and treatment. Samples analyzed derive from many facilities and researchers and approximately 2600 samples were analyzed on the JEOL and over 2000 on the MALDI instrument.